Electronic apparatus such as a computer, a mobile phone terminal, a portable information terminal, and a tablet terminal displays information to a user with characters and images on its display screen. In particular, with high performance and multiple functions of such portable information terminals, an amount of information displayed with characters and images on the display screen of the portable information terminal has been increased. However, since the size of the display screen mounted on the portable information terminal is limited, the characters and the images to be displayed become small when a lot of information is displayed with characters and images on the display screen. When it is difficult for the user to read the small character, it is desirable that an operation to change a display scaling factor of the character and the image is performed.
The states of eyes of users include nearsightedness, farsightedness, presbyopia, and the like. Therefore, a technique has been discussed by which the fatigue of eyes of user is reduced by registering the state of the eyes of the user beforehand and displaying characters and images in appropriate size corresponding to the registered eyes state (Japanese Laid-open Patent Publication No. 2007-10924). In addition, there is a technique by which it is detected whether or not a user wears glasses. The technique has been discussed in Japanese Laid-open Patent Publication No. 2006-318374.